Loud speaker



Jan. 8, 1929.

C. P. MADSEN LOUD SPEAKER Filed Dec. 50,. 1925 5 Shgets-Sheet 1 VIII/III/7/A III/111111,

INvENToR (away Jan. 8, 19 29.

c. P. M ADSE N LOUD SPEAKER Filed Dec. 30, 1925 5Shets-Sheet 2 I INVENTOR V BYOB/M1114 ATTdRNEY Jan. 8,1929; 1,698,504

' c. P. MADSEN LOUD SPEAKER 1 "Filed Dec. so, 1925- sspeets-sneet 3 IINVENTOR W (P. .MAAM' 6 54 1 ATTORNEY Jan. 8, 1929.

C. P.1MADSEN LOUD SPEAKER 5 Sheets-Sheet 5 Filed; Dec. 50, 192,5,

Fig. 15

ATTORNEY Patented Jan. 8, 1929.

v UNITED s'rAr PATENT OFFICE.

cums r. MADSEN', on NEW YORK, N. Y., A$SIGNOR, BY'MESNE ASSIGNMENTS, r

- WILLIAM w. w nner, on BALTIMORE, MARYLAND. v

noun srE K'ER.

Application filed December 30, 1925. Serial No. 78,492.

I This invention relates to telephone appa- I bly. It is intended primarily for use in connection with radio apparatus, but it can also,

" be used in connection with ordinary telesystems, and it is also adaptable-for use as a v in the cone itself; I have discovered that if fying sound on ordinaryphonographs.

phone apparatus known as public address means of stepping up the volumeor' ampli- There have heretofore been in use two gen eral types of apparatus both depending upon diaphragm action. In one case a very small diaphragm is used and a horn or other means provided for amplifying the sound. In the other case a very large diaphragm is used in the nature'of a cone fastened at its edges either with o'r' without a hinge and known to physicists as the tympanum. These apparatuses have serious faults. Both of the diaphragms possess a fundamental note together with harmonies which are not of a musical frequency, the results being that the music or the speech reproduced is highly distorted. In the case of the small diaphragm there is in addition what is known as horn'eifect; in the case of the large diaphragm very serious mechanical difficulties are encountered. Since the large diaphragm isifastened at its edge to a fixed support and at its apex to. the actuating means, any change in the size or shape of the diaphragm'due to moisture or temperature affects the actuating means.

throwing it out of adjustment. 7

My invention may have the appearance of thelarge diaphragm type but the similarity is only superficial. It is well known that any body in order to produce or reproduce sound must possess resilience. The reason is that bodies of matter which can be used possess a certain degree of, inertia and unless aresilience is opposed to the inertia; the sound will be dampened. In the-case of the large diaphragm telephone reproducers; this resilience is provided by the cone or .thehinge a resilience is provided at the source of motion sufficient to balance the inertia of the wholesystem that then no resilience need by provided'in the cone nor its fastening and I produce in this manner sounds with any body which is sufficiently light and will maintain its shape. iii:

The object of this invention is to provide simpleand improved means and structures for utilizing the new method of generating air waves of sound frequency disclosed in my co-pending application electrically actuated, said '-copending' application being Serial Number 27,206.

This method consists briefly in providing a relatively thin but rigid body'of relatively large area with the proper degree of resilience near its support. The body may be of any form ,which will maintain its shape but I preferably use a cone, in which case it is supported from theapex only and a resilience is provided at the supporting point.

Referring to my pending application, which is provided with a needle for phonographic reproduction, in place thereof in this invention I provide an iron armature at the point. where the needle usually goes and actuate it by an electro-magneticsystem; Any of the several types of the well known electrio magnetic systems may be used, as for instance thesmgle acting system such as is used in ordinary ear phones, or the,push and pull magnetic system such as is used for alternating current, or the electro dynamic systems. I have found that my invention enables me to get proportionately greaterresults over the old art with the ordinary single actingsystem such as is used in an ordinary telephone receiver. A great fault of that system, when used in the old Way with-a diaphragm being that when used with direct current such as supplied by an ordinary amplifying tube the diaphragm is pulled from one side only and 'must return by its own resilence and therefore the reproduction is faulty. A part'of my invention consists-in providing the necessary resilience without the diaphragm.

I further object of my invention is the providing an improved loud speaker, electrically operated, of extreme sensitiveness.

A further object of my invention is the providing a loud speaker of cheap construction, simple and effective in operation.

A further object of myinvention is the providing an improved sound producing device electrically operated by electrical effect, operating on a unit structure sound generatingmeans.

A further object of my invention is the providing in a loud speaker improved means of supporting sound producing device electrically operated.

A further object of my invention is the method of producing air waves of sound frequency by electrical impulses operating on a unit structure producing a torsional effect in the support thereof.

In the drawing of the herein described embodiment of my invention, Fig. 1 is a sectional view in elevation of the preferred embodiment of my invention in' which the actuating means is an ordinary bipolar electric unit, such as is now commonly used'in ear phones and in many types of loud speakers; Figure 2 is a plan view of the loud speaker shown in Figure 1, with certain parts omitted; Figure 3 is a detailed view of the supporting means-between the armature and p to keep ,the same insulated from the case and I do'this by placing between these parts and its support; Figure 4 being a View taken at rlght angles to the view shown in Figure 3;

Figure '5 is a View similar to that shown in Figure 1,, 1n WlllCll I have shown a modified means of-supporting the armature; Figure 6'being a plan View of the modified reproducer shownin-Figure 5 and is a view somewhat similar to Figure 2; Figure 7 is a view-in elevation in section of a modified form as adapt: ed to a push and pull or rocker type of electric unit as may be found in existing loud speaking telephones intended for alternating current; Figure 8 being a reduced view in elevation of that shown in Figure 7 Figure 9 is an enlarged view in elevation in section of the bipolar unit shown in Figure l taken at right angles to said view; Figures 1011 1213 are enlarged views of details which will be described hereinafter; Figure 14 is an enlarged View in section in elevation taken at right angles to the view shewn in Figure '7 of the pull and push mechanism; Figures 1516.17 being enlarged fd etails of said" mechanism, and Figure 18 being an inverted plan view of the same.- Similar numerals-refer to similar parts throughout the several views.

Referring particularly to Figure 11 is I the base or supporting plate; 2 and 2' are the permanent or horse-shoe magnets, on which rest soft iron pole pieces 2"2, around which are the wire bobbins 3 and-3. lOrdinarily the support of the magnets and bobbins are maderigid or integral with the ease. I have discovered that it is very much better the case a resilient preferably-a vulcanized rubber. cushion 4, which rests on the bottom of the supporting frame 5; 6 is a screw threaded into supporting frame 5 and bears under washer 7 and is provided withhandle. f 7

- The. object of this arrangementis to provide a means of adjusting very accurately the gap or distance between the pole pieces2 and 2 and the armature 8 to permit of the use of j different. vol es. armature 8, which is preferablymade of soft Norway iron, is slotted at one end. In this mean In the preferred form slot is inserted a piece of clock spring 10, the opposite end of said spring being inserted in a slot in block 9. The distance between armature 8 and block 9 determined very accurately for correct-response by trial. After this distance has been determined, the 'twoparts are adjusted to it and then integrally united v 11 is a smalLn-ietal cone, preferably dur aluminum, fastened to armature 8, and 12 is the oscillator which is preferably'made of bakelite dielecto or vulcanized fibre and may be ofa' size depending on the power of the electrical-unit With units of such" size as are connnonly-used I find the oscillator, 12, works-most efficiently when about '12" in diameter.

' FiguresB-Q show in greater detail a modie fication of the means of supporting arma ture .8 with the; same type of unit. In this modification instead of using a clock spring I provide the armature 8 with a spindle 13,

which is surrounded by an organic resilient material, preferably vulcanized rubher,,in a

.high state of tension, This material is initial.-

ly tensed, as for instance, forcing on a rubber tube whose inside diameter is smaller than that of the spindle, or windingit very tautly with a rubber band. Ilhis wound spindleis then compressed between blocks 15 and 16 1100 by means of screws 17. I This structure is not; r so permanent as the preferred form but lends itself to extremely accurate adjustment-for 7 correct response. I

In Figures 13 and 14 is shown'a structure of the cone llwhen it is desired to make osci-llator 12'removable'. This cone 25 is provided with Figures 1016showthe embodiment of my invention with what is known as the Fpush aninside coneand a swivel telephone intended for alternating current. In this unit 20 and 20' are soft iron pole pieces fastened to the permanent magnet 21. 22 and 22 are the bobbins and 23'isthe armature. The action of this type of unitis too well knownto need description here. Instead however of supporting this-armature in the I usual way I support" it byinea'ns of spindle 24 in blocks 25; Bath 'nd 'of the spindle" is.

"by screws 26. .Blooks25 rest upon platform by means of screws 28, which provide a sof centeringarmature 13 between the pole pieces;

One end of armature 13 is provided with stud 29 upon the upper end of which are cones 11 and 18,.between which is clamped and pull ori .r rockerltype of loud. speaking the Oscillator 12. The size of this oscillator may, in this unit, be much larger than that used in the two other' structures. found that this type of electricalunit when connected with an adequate electrical supply will operate an oscillator two feet in diameter.

In my 'improved loud speaker I avoid the error due to moisture absorption by the diaent is- L LA loud speakercomprising a support in which an armature s fulcrumed or oursound more reliable.

Having thus described my invention, what desire to secure by Letters Pat- 4 phragm, alsothe effect of temperatureupon the same and have found that by using a cone whose edge is free and unobstructed the response is much freer and distortion less and I claim and tively adjusting said armaturewith reference to the efl'ect of said magnetfconsisting of an organic resilient member between said magnet and said case and means of varying the tension of said organic resilient member' to adjust the magnet.

3. In an. organized loud speaker provided with an armature, an air vibrator free to vibrate in unconfined space attached to and entirely supported by said armature an electric magnet and a supporting case for the same, and means of adjusting relatively the I have:

position of said armature and said magnet consisting of adjusting means to adjust said magnet with reference to said supporting case 511:1,

4:. In anorganlzedloud speaker provided .with an armature," an' a-ir vibrator attached to and entirely supported by said armature, an electric'magnet' and a supporting means for the SiLHIBgfiIld means for adjustingrela- .tively the position of said armature and said magnet consisting of an organic. resilient member between "said magnet and said supporting means and means for varying the tension of said organic resilient member to adjust the magnet. p

5. In an organized loud speaker provided with a magnet and an armature under the influence of said magnet an air vibrator free to vibrate in unconfinedspace attached to and entirely supportedby said armature, a support for said magnet and said armature relatively' positioning the same, adjustable means for tensioning the supporting ofsaid armature to eflect the freedom of the vibration thereof while under the influencesof said magnet. H v v 6. In an organized loud speaker provided with a magnet and an armature under the influence of said magnet, an air vibrator free to vibrateih unconfined space attached to and entirely supported by said armature, a support for said magnet and said armature relatively positioning-the same, adjustable means for tensioning the supporting of said armature to effect-the freedom of the vibration thereof while under the influence of said magnet consisting of tightening the holding means'of said armature to decrease the freedom of movement thereof.

CHARLES P. MADSEN. 

